Whatever the level of mutilation and finger concerned, carrying out a digital amputation is a significant surgical procedure with functional consequences. We speak of “temporary” amputation when a subsequent reconstruction is planned. This is most often a microsurgical reconstruction by toe transfer. In these circumstances the surgical principles governing fashioning the stump are different from those observed when the digital amputation is permanent. It is therefore crucial to understand the surgical strategy as a whole.
As for all surgical procedures, a digital amputation should be performed whenever possible in a single stage. It is important to fashion a satisfactory stump.
A functional stump must have a mechanically adapted skin cover. Excessive soft tissue leading to a floppy digital stump must be avoided. This is unattractive and is furthermore not functional because of excess soft tissue mobility. At the other end of the spectrum, inadequately covered stumps with thin and adherent skin are often painful during grip.
The existence of pain in a digital stump very often leads to its gradual exclusion. Obtaining a painless stump requires specific treatment of the digital nerves. Proximal resection of the palmar digital nerves alone, however, is an insufficient guarantee if the skin and bone are not addressed with proper surgical techniques.
A functional digital stump must have adequate sensation, which excludes a priori certain skin coverage solutions such as remote flaps, which at best only give a protective sensibility in the long term. Obtaining a sensitive stump is the result of a careful choice regarding closure and skin cover technique. Indirectly the sensibility obtained in the stump depends on the level of bone shortening. Depending on the clinical scenario, length should be preserved, even using a sensitive flap for coverage of the stump. On the contrary, some situations require shortening so as to allow closure by the simple apposition of two skin flaps, dorsal and palmar.
The mobility of a digital stump depends partly on the integrity of the joints proximal to the stump and partly on the existence of motor tendons. Mobility is also linked to the level of bone shortening. When only a short segment from the base of a phalanx persists, even if the tendon insertions are intact, the mobility obtained will have little clinical utility, given the shortness of the lever arm.
Amputations at Terminal Phalanx
The chapters dedicated to pulp defects and nail trauma emphasized the functional importance of the distal phalanx and technical possibilities for reconstruction. It has been clearly demonstrated that when describing techniques for digital replantation, the most distal of these replantations at the level of the terminal phalanx gave the best functional outcomes. However, there are circumstances where a permanent amputation is the only possible technical solution. For these distal digital amputations, we have never performed a subsequent transfer of the second toe to reconstruct the terminal phalanx, because the functional and aesthetic results of these surgeries seem questionable. In the distal phalanx, amputation will therefore always be permanent.
As we will see, amputations through the distal phalanx of the thumb are sometimes an exception to this rule. In zones I, II and III ( Fig. 12.1 ), all attempts to preserve the remaining length of the distal phalanx must be made. The different sensitive flaps that can be used to cover the bone have already been described. Treatment of the nail complex also depends on the level of amputation. Preservation of this may be considered in zones I and II, validating complex reconstruction techniques depending on the case, making use of nail bed grafts or flaps. However, in zone III it is not realistic to hope to restore a nail bed of sufficient length. Under these conditions the shortness of the bed inevitably leads to a functionally cumbersome hook-nail deformity if the nail matrix is preserved. At this level it is therefore imperative to permanently sterilize the nail matrix in the first instance. There is nothing more frustrating for the surgeon than to have to intervene again iteratively to resect the troublesome nail remnants. This excision must therefore be meticulous, using magnification, raising a skin flap from the dorsum of the proximal nail fold to radically excise the whole germinal matrix.
When the amputation is very proximal and only a few millimeters of the terminal phalanx persist, it not useful and even contraindicated in functional terms to preserve the base of this phalanx. Even with its normal tendon insertions preserved, the shortness of the bone segment will not confer any functionally useful mobility to this phalangeal remnant. Under these conditions it is better to immediately proceed to an amputation at the level of the head of the middle phalanx, which will also simplify the skin closure ( Fig. 12.2 ).
Amputations at Middle Phalanx
Amputations Through Head of Middle Phalanx
This is the ideal level of amputation. The entire length of the diaphyseal segment of the middle phalanx is preserved, conferring good functional effectiveness of flexion and extension of the proximal interphalangeal joint. The outline of the skin flaps is asymmetric, favoring when possible the palmar flap at the expense of its dorsal counterpart. Doing so transfers the suture line to the dorsal aspect of the finger, obtaining cushioning of the digital extremity by thick glabrous skin, better adapted for grip. The bone is addressed by shaping the distal end of the middle phalanx with a rongeur. The prominence of the lateral condyles is gradually shaved down. This is essential and results in a stump of acceptable morphology to be formed.
The deep flexor tendon is retrieved using fine forceps inserted into the flexor sheath; this tendon is then drawn proximally and sectioned, then allowed to retract freely. In the extensor apparatus the two lateral bands are resected proximal to the bone end. The flexor and extensor tendon elements should never be sutured to one another; this risks creating the quadriga syndrome described by Verdan.
At this stage of the procedure the neurovascular bundles must be found and dissected. Each artery is ligated or coagulated, and each nerve is dissected with the aid of gentle axial tension. The nerve thus exteriorized in the wound will then be cut proximally and then allowed to retract in a safe area so that its extremity is not surrounded by sclerotic scar tissue. Finally, both skin flaps are apposed. Additional skin resection may be necessary to obtain a harmonious profile.
Amputations Through Middle Phalanx Diaphysis
Whenever the initial amputation has occurred distal to the insertions of the superficial flexor, preservation of the residual middle phalanx diaphysis is indicated. Under the effect of the still-intact superficial flexor and the central slip of the extensor inserted on the base of the middle phalanx, the finger will have useful function during grip. The amputation technique is similar to that previously described with regard to the outline of the skin flaps, the proximal resection of the deep flexor and the treatment of neurovascular bundles. However, when the amputation occurs at a more proximal level to the insertion of the superficial flexor tendon, conservation of the middle phalanx is more questionable. When there is sufficient soft tissue to allow preservation of length without further difficulty, conservation of the middle phalanx can be considered, more for aesthetic than functional concerns. However, it would not seem appropriate to propose a sophisticated technique of skin coverage using a neighboring flap to preserve at all costs a base of middle phalanx devoid of its tendon insertions and not functionally useful ( Figs. 12.3–12.5 ).